Cellulosic material and product obtained therefrom



P atente'cl Jan. '8, 11929.

HENRY DREYFUS, OF LONDON, ANDCLIFFORD IVAN BY, ENGLAND, ASSIGNORS-TOOELANESE CORPORATION OF AMERICA, A GORPORA- 'TION OI DELAWARE.

OELL'ULOSIC MATERIALAND PRODUCT OBTAINED THEBEFBJOM.

No Drawing. Application filed January 19, 1927,

This invention relates to the treatment of cellulosic materials for thepurpose of rendering them more reactive for esterification andespecially acetylation and also to the production of cellulose acetatesor other cellulose esters from said treated materials.

We have now discovered that cellulosic I materials can be rendered moreeasily esterifiable by treatment with small quantities.

of formic acid.

Theuse of small proportions of formic acid is especially valuab e inthat it is not necessary to subject the cellulosic material to an aftertreatment for the removal of the formic acid, such as is necessary inthe case where larger proportions of formic acid are used. ,As will bereadily understood, in the case where the cellulosic materials areacetylated directly after pretreatment with formic acid, the formic acidin the cellulosic material is destroyed by the acetylating medium usedin the subsequent acetylation,

. the acetic anhydride being simultaneously converted into acetic acid.This by-reaction would occasion a considerable wasta e'of aceticanhgdride where large quantitles of formic aci are present, but the lossof acetic 'anhydride is relatively small when only small quantities'offormic acid are present.

By the use of small quantities of formic acid in the pretreatment itbecomes possible therefore to proceed directly to the esterification ofthe cellulosic material, without any intermediate treatment for theremoval of formic acid b' evaporation, or by washing with water ollowedby a drying operatlon, or by other methods.

Good results are obtained by the use of 10 to 20 parts by weight offormic acid to each 100. parts by weight of cellulosic materials,though'the proportions of formic acid used may be greater or less thanthose indicated. In using very small proportions of formic acidcare-must be taken to ensure that the cellulosic materials are evenlymoistened with the formic acid, while the use of formic acid inproportions exceeding 20 or at most I 30% of the cellulosic materialonlyfleads to an increase in the wastage of acetic ,anhy dride withoutany material advantage in other directions. I The formic acid may beemployed in a concentrated form or diluted with water Serial No.162,218, and in Great Britain October 8, 1928.

nanny, or sronnon, NEAR nnnor other diluent. For instance, 100% formic Iacid, or aqueous solutionsfcontaining. 50- 100% preferably 70-90% beused, or mixtures 'of formic acid and acetic acid many desiredproportion may also be employed.

As cellulosic materials, we employ cotton, cellulose (in either themercerized or the nonmercerized form) or wood pulp, the latter havingbeen preferabl first submitted to an alkali treatment $110 as indicatedin the British specification No. 249,17 3 and corresponding U. S.application S. No, 747,054,

formic acid, may

or other cellulosic materials or their converslon products. Thecellulosic material used may contain the usual amount ofmoisture forexample, 4% to 6% or 8%, or maybe freed from moisture by drying.

In practising the. invention, the formic acid is distributed evenly overthe cellulosic material, for instance, by spraying, the cellulosicmaterial being turned or moved from time to time if necessary to ensureuniformimpregnation with the formic acid. The cellulosic material isthen allowed to stand until a product capable of rapid esterification isobtained.

The time occupied varies with the nature of the cellulosic material, theconcentration of the formic acid, the temperature at which thecellulosic material is maintained, and

the degree of reactivity required in the product. The treatment proceedsquite satisfactorily at ordinary temperatures but may if desired beaccelerated by the use of increased temperatures. p

In the subse uent esterificatipn due allowance should e made for thedestruction of theesterifying agent by the formic acid present and any.;water introduced therewith, particularly when workingby processes inwhich minimum quantities of the esterifymg medium are used. Thus inacetylation processes, the amount of acetic anhydride is increased by anamount suflicient to convert the water formed by decompositionof theformic acid, together with any water mixed therewith, to acetic acid.

The products may-be acetylated with ease and rapidity by any of theusual processes employed for this purpose, provided that the proportionof acetic anhydride is increased in the manner previouslyindicated, theprortion of acetic acid added being preferably.

iminished by an amount corresponding wi that formed from theexcess ofacetic anhydride employed.

The treatment may be. efiected in the manner described in the followingexample, it being understood however, that this example is not to beregarded as limiting the inventioninanyrespect.

- Example 1-. 100 parts of cellulose dried or conta' g for instance 5-6%of moisture, are spraye with about 15 parts of 7 585% formic acid. Thecellulose is allowed to stand'until the desired degree of reactivity hasbeen reached, for instance for 8-12 hours, and is afte" wards added toan acetylating bath.

I Example 2.

100 parts of cellulose, dried or containing 56% of moisture, aremoistened with about 20 parts of a mixture containing -40% of formicacid'and -70% of acetic acid.-

After the desired degree of reactivity has developed, the celluluose isacetylated.

The acetylation suitable process, and especially by the processesdescribed in British specifications Nos. 14,101 of 1915,

101,555, corresponding U. S. Patents Nos.

1,278,885, 1,280,974 and 1,280,975, British- 207,562 and correspondingS. application S. No. 633,016 filed 18 April, 1923, but in the case ofcellulose that has been pretreated in accordance with the gpecificationNo.

foregoing example we use about 50 additional parts b weight of aceticanhydride to compensate or the wastage which takes place as the resultof the formic acid in the cellulose.

Thus, to aoetylate 100 parts of pretreated cellulose, we ma use 900to1000 parts by weight of glacia acetic acid, 10 to 15 parts by weight ofparts by weight of acetic anhydride.

What we claim and desire to secure by Letters Patent is 1. A rocess fortreating cellulosic'material w ich comprises treating said cellulosicmaterial with a small proportion of formic acid, thereby producing acellulose which is highly reactive for esterification.

2. A rocess terial w 'ch comprises treating said cellulosic materialwith a small proportion of an aqueous solution of formic acid, therebyproducing a cellulose which is highly reactive for esterification. I

8. Apfocess for treating cellulosic material w "ch comprises treatingsaid cellulosic material with a small proportion of formic acid of atleast 50% concentration, thereby ly reactive for esterification.

.a mixture containin may be performed by any presence of the sulphuricacid and 250 to 300 for treating cellulosic maproducing a cellulosewhich is high- 4. A rocess for treating cellulosic material whichcomprises treating said cellulosic material with a small proportion offormic acid of at least concentration,

thereby producing a cellulose which is highly reactive foresterification.

5. A rocess for treating cellulosic material w 'ch comprises treatingsaid'cellulosic material with a small proportion of formic and aceticacids, thereby producing a cellulose which is highly reactive foresterification.

6. A process terialwhich comprises treating said cellulosic materialwith a small pro ortion of an aqueous mixture containing ormic andacetic acids, thereby producing a cellulose which is highly reactive foresterification.

7. A process for treating cellulosic material which comprises treatingsaid cellulosic material with a small proportion of for treatingcellulosic ma- 0 an aqueous mixture containing at least 50% v of formicand acetic acids, thereby producing a cellulose which is highly reactivefor esterification.

8. A process for treating cellulosic material which comprises treatingsaid cellulosic material with a small proportion of an acqueous mixturecontaining at least 70% of formic and acetic acids, thereby producing acellulose which is highly reactive for esterification. I

9. A process for treating cellulosic material which comprises treatingsaid cellulosic material with a proportionnot exceeding 30%, calculatedon the weight of the cellulosic material, of an'a'cqueous solution offormic acid, thereby producing a cellulose which is highly reactive foresterification.

10. A process for treating cellulosic material which comprises treatingsaid cellulosic material with a proportion not exceed-' ing 30%,calculated on the weight of the co ulosic material, of an aqueoussolution offormic acid, thereby producing a cellu-- lose which is highlyreactive for esterification.

11. A process for treating cellulosic'material which comprises treatingsaid cellulosic material with a proportion not exceedin 30%, calculatedon the weight of the I ce ul osic material, of a mixture containingformic and acetic acids, thereby producing a cellulose which is highlyreactive for esterification'.

and subjecting the resulting cellulose to the actionof an medium.

13. A process for treating cellulosic material which comprises.treating; said cellu- ,12. A process for treating cellulosic malosicmaterial with a small proportion of an aqueous mixture containing formicacid, thereby producing a cellulose which is highly reactive foresterification, and subjecting the resulting cellulose to the action ofan esterifying medium.

14. A process for treating cellulosic material which comprises treatingsaid cellulosic material with a small proportion of a mixture containingformic and acetic acids, thereby producing a cellulose which is highlyreactive for estcrification, and subjecting the resulting cellulose vtothe action of an esterifying medium.

15. A process for treating cellulosic material which comprises treatingsaid cellulosic material With a small proportion of formic acid, thereby.producing a cellulose which is highly reactive for. esterification, andsubjecting the resulting cellulose to the action of an esterifyingmedium for the production of carboxylic acid esters.

16. A process for treating cellulosic material which comprises treatingsaid cellulosic material with a small proportion of formic'acid, therebyproducing a cellulose which is highly reactive for acetylation, and

subjecting the resulting cellulose to the action of an acetylatingmedium.

17. A process for treating cellulosic material which comprises treatingsaid cellulosic material with a proportion not exceeding calculated ontheweight of the cellulosic material, of an activating agent comprisingformic acid, thereby producing a cellulose which is highly reactive foracetylation, and subjecting the resulting cellulose to the action of anacetylating me dium. I

18. A process for treating cellulosic material which comprises treatingsaid cellulosic material With a proportion not exceeding 30%, calculatedon the weight of the cellulosic material, of-an activating agentcomprising formic and acetic acids, therebyproducing a cellulose whichis highly reactive for acetylation and. subjecting the resultingcellulose to tlie action of an acetylating medium.

In testimony whereof we have hereunto subscribed our names.

-HENRY DREYFUS.

CLIFFORD IVAN HANEY.

